November 27, 2015

Homework Help: Chem

Posted by Anonymous on Monday, May 7, 2007 at 6:15pm.

Calculate the concentration of NH4+ from ammonium chloride required to prevent the precipitation of Ca(OH)2 in a liter of solution that contains .10 mol of ammonia ans .10 mol pf calcium ion.
I got the two equations but I do not know where to begin.

The question asks for (NH4^+) yet you give an answer in Ca ion which doesn't make sense. Could you have meant that the solution contains 0.1 mol Ca ion?

yes .1 M Ca ion and .1 M ammonia

Ksp Ca(OH)2 = (Ca^+2)(OH^-)^2 =??
Kb = (NH4^+)(OH^-)/(NH3) =??

From equation 1, calculate (OH^-) needed for pptn with 0.1 M Ca ion.

From equation 2, using 0.1 M for (NH3), and the (OH^-) from equation 1, calculate (NH4^+).

Post your work if you get stuck.

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